.\" Copyright (C) 2022 Jens Axboe <axboe@kernel.dk>
.\"
.\" SPDX-License-Identifier: LGPL-2.0-or-later
.\"
.TH io_uring_prep_poll_timeout_update 3 "March 12, 2022" "liburing-2.2" "liburing Manual"
.SH NAME
io_uring_prep_timeout_update \- prepare a request to update an existing timeout
.SH SYNOPSIS
.nf
.B #include <liburing.h>
.PP
.BI "void io_uring_prep_timeout_update(struct io_uring_sqe *" sqe ","
.BI "                                  struct __kernel_timespec *" ts ","
.BI "                                  __u64 " user_data ","
.BI "                                  unsigned " flags ");"
.PP
.BI "void io_uring_prep_timeout_remove(struct io_uring_sqe *" sqe ","
.BI "                                  __u64 " user_data ","
.BI "                                  unsigned " flags ");"
.fi
.SH DESCRIPTION
.PP
These functions modify or cancel an existing timeout request. The submission
queue entry
.I sqe
is setup to arm a timeout update or removal specified by
.I user_data
and with modifier flags given by
.IR flags .
Additionally, the update request includes a
.I ts
structure, which contains new timeout information.

For an update request, the
.I flags
member may contain a bitmask of the following values:
.TP
.B IORING_TIMEOUT_ABS
The value specified in
.I ts
is an absolute value rather than a relative one.
.TP
.B IORING_TIMEOUT_BOOTTIME
The boottime clock source should be used.
.TP
.B IORING_TIMEOUT_REALTIME
The realtime clock source should be used.
.TP
.B IORING_TIMEOUT_ETIME_SUCCESS
Consider an expired timeout a success in terms of the posted completion.
Normally a timeout that triggers would return in a
.B -ETIME
CQE
.I res
value.
.PP
The timeout remove command does not currently accept any flags.

.SH RETURN VALUE
None
.SH ERRORS
These are the errors that are reported in the CQE
.I res
field. On success,
.B 0
is returned.
.TP
.B -ENOENT
The timeout identified by
.I user_data
could not be found. It may be invalid, or triggered before the update or
removal request was processed.
.TP
.B -EALREADY
The timeout identified by
.I user_data
is already firing and cannot be canceled.
.TP
.B -EINVAL
One of the fields set in the SQE was invalid. For example, two clocksources
were given, or the specified timeout seconds or nanoseconds were < 0.
.TP
.B -EFAULT
io_uring was unable to access the data specified by
.IR ts .
.SH NOTES
As with any request that passes in data in a struct, that data must remain
valid until the request has been successfully submitted. It need not remain
valid until completion. Once a request has been submitted, the in-kernel
state is stable. Very early kernels (5.4 and earlier) required state to be
stable until the completion occurred. Applications can test for this
behavior by inspecting the
.B IORING_FEAT_SUBMIT_STABLE
flag passed back from
.BR io_uring_queue_init_params (3).
.SH SEE ALSO
.BR io_uring_get_sqe (3),
.BR io_uring_submit (3),
.BR io_uring_prep_timeout (3)
